As a basic structure of a conventional solid polymer electrolyte fuel cell, there is one disclosed in Japanese Patent Application Laid-Open No. H6-260193 (1994). In the conventional membrane electrode assembly (MEA), catalyst layers, which contain precious metals (mainly platinum), are formed on both main surfaces of a solid polymer electrolyte. Porous material layers, which introduce a reactive gas to the solid polymer electrolyte, are further arranged on the outsides of the catalyst layers. Further, on the outsides of the porous material layers, separators are arranged. In the separators, anode-side separators and cathode-side separators are present. On one surface of the anode-side separator, fuel gas passages are formed, and on the other surface thereof, coolant passages are formed. In the cathode-side separators, oxidizing gas passages are formed. Unit cells, each being formed by constituent elements as described above, are sequentially stacked, and thus a fuel cell stack is constituted.